1. Field of the Invention
This invention relates to a motion picture projector, and more particularly to a telecine projector by which a film can be advanced at an arbitrary preselected speed and projected at a speed corresponding to the video field rate.
2. Description of the Prior Art
Generally, the film advance rates of a cinema film and an 8 mm-film are 24 frames per second or 18 frames per second. A field frequency of a television signal is sixty fields per second for the NTSC system, and fifty fields per second for the SECAM or PAL system.
A so-called "telecine projector" is required for reproducing the picture of the cinema film or 8 mm film on the screen of a television receiver.
Classifying roughly, there are an intermittent type and a continuous type of telecine projector. For example, a so-called 2/3 pull-down method telecine projector of the intermittent type is widely used in conjunction with the NTSC system. In the 2/3 pull-down method, one film-frame is advanced and held for two television fields and then the next frame is advanced and held for three television fields. It is in principle impossible to effect fast motion reproduction or slow motion reproduction or to use film at a rate other than 24 frames per second. Therefore, a telecine projector of the continuous type is used for the fast motion reproduction and the slow-motion reproduction.
There are a rotary mirror and a rotary prism types of the telecine projector of the continuous type. In both types, the picture on the running film is supplied to a television camera as a still picture which is converted to a television signal. Fast motion reproduction or slow-motion reproduction can be effected by changing the film running speed.
However, the rotary mirror type and the rotary prism type have the disadvantage of wow in the film running and of picture distortion due to the fluctuation of the film advance pitch. The picture becomes distorted due to the inacurracy of the rotary prism in the rotary prism type. Moreover, the color of the picture becomes deteriorated due to the dispersive property of the prism disposed in the optical system. The projector of the rotary mirror type is complicated in construction. Moreover, the rotary mirror type projector has the same disadvantage as the projector of the rotary prism type in picture distortion.